You did not mention if you are in a Cmd-generated app or not. If you are then try "sencha app build" instead as it contains a lot more than just the JS compile step.

If you are not in a Cmd-generated app and if you code does not fully specify it "requires" then it will probably help to tell the compiler which framework you are using (to enable its auto-dependency checks which are framework-specific). That switch should also automatically add the "src" folder to the classpath.